The present invention relates to a display device, and more particularly to an active matrix type display device which forms a matrix array by making gate lines and data lines cross each other on one of two substrates and includes storage lines which constitute storage capacities for holding lighting of pixels.
Liquid crystal display devices have been widely used as display devices of notebook type personal computers, various monitors or various other information equipment. Particularly, as display devices of portable telephone sets or portable information terminals referred to as PDA, the liquid crystal display devices have been used in view of characteristics thereof that the devices are small in size and light-weighted and exhibit the low power consumption. Further, the liquid crystal display devices each of which directly mounts a driving circuit chip on a portion of the substrate thus realizing the miniaturization as a whole have been spreading as a main stream.
In many cases, the liquid crystal display device which is adopted by this type of portable information terminal is constituted to supply display data and driving voltages from one side of two laminated substrates in view of the reduction of mounting space and easiness of mounting of a control circuit. Particularly, the liquid crystal display device for portable telephone set adopts, in many cases, a method in which a flexible printed circuit board is mounted on one side of two substrates for supplying display data and other driving voltages for facilitating the accommodation of parts in a limited mounting space.
Although various types of liquid crystal display devices have been known depending on the constitution of electrodes and driving methods, here, a liquid crystal display device which is generally referred to as a TN type is explained as an example. In this TN type liquid crystal display device, a display region is formed by sealing liquid crystal in a gap defined by laminating a first substrate and a second substrate which constitute a pair of substrates. On the display region of the first substrate, a matrix is constituted of a large number of data lines (also referred to as drain lines, signal lines or the like) which extend in the longitudinal direction (referred to as first direction hereinafter) and are arranged in parallel in the lateral direction (referred to as second direction hereinafter) and a large number of gate lines (also referred to as scanning lines or the like) which extend in the lateral direction which crosses the data lines at a right angle and are arranged in parallel in the longitudinal direction, and a pixel is formed in a region surrounded by a pair of data lines and a pair of scanning lines.
The second substrate includes counter electrodes which face pixel electrodes in an opposed manner and are served for applying an electric field to the liquid crystal of the pixel. In color display, the second substrate also usually includes color filters of three colors. Each pixel is formed of the liquid crystal which is sandwiched between the pixel electrode provided to the first substrate and the counter electrode provided to the second substrate and lighting/non-lighting of the pixel is controlled by turning on/off a switching element (typically a thin film transistor; TFT, referred to as thin film transistor hereinafter) formed at a corner of the pixel.
To hold a voltage of display data when the thin film transistors which constitute these pixels are turned on for a given period, storage capacities (Cstg) are provided to respective pixels. Although various methods have been known as methods for supplying electricity to these storage capacities (that is, storing charge of display data supplied to the pixels and holding the charge for a given period), there has been known a method which provides lines referred to as storage lines in a display region. These storage lines are usually formed close to and parallel to respective gate lines on the first substrate.
In plane, on the display region, the storage lines are alternately positioned between the scanning lines and extend in the direction parallel to the extension direction of the scanning lines. Further, the storage lines have one ends thereof connected to a common line and the common line is pulled around to be connected to a given terminal formed on one side of the substrate. Conventionally, mounting of gate lines and storage lines in this type of liquid crystal display device has been performed in a following manner. Here, the explanation is made assuming a liquid crystal display device which is configured such that a driving circuit mounting region, that is, a driving circuit chip mounting region is provided to the first substrate, the second substrate overlaps a portion of the first substrate except for the driving circuit mounting region, and a periphery of the overlapped portion is sealed with a sealing member. Further, the explanation is made assuming that the above-mentioned driving circuit mounting region is arranged at the longitudinally lower side (lower side) of the liquid crystal display device. Accordingly, two sides of the first substrate which are disposed adjacent to the lower side of the first substrate having the driving circuit mounting region are referred to as a left side and a right side.
When the data lines are formed in the first direction (longitudinal direction, for example) of one substrate (the above-mentioned first substrate, also referred to as a thin film transistor substrate) of the liquid crystal display device which is constituted by laminating two substrates, the gate lines are formed in the second direction (lateral direction, for example) which cross the data lines at a right angle. The gate lines are extended along one side (left side, for example) in the lateral direction, that is along the left side of the substrate, for example and are pulled out to the above-mentioned driving circuit mounting region. On the other hand, the storage lines are formed between the above-mentioned respective gate lines and are pulled out to the above-mentioned driving circuit mounting region along the other side (right side, for example) in the lateral direction, that is, the right side of the substrate by way of the common line.
However, when the gate lines are pulled out at only one side (only a picture frame region at the left side, for example) as in the case of the prior art, the width of the left-side picture frame region and the width of the right-side picture frame region differ from each other and hence, the display region is arranged such that the display region is offset to the right from the lateral center position on the substrate.
Accordingly, by dividing the gate lines into a group of gate lines which is pulled out from the left-side picture frame region and is extended in the direction toward the lower side and a group of gate lines which are pulled out from the right-side picture frame region and is extended toward the lower side and, thereafter, by pulling out these gate lines using both of left and right picture frame regions, the display region can be arranged at the center position in the lateral direction. However, in such an arrangement, when the common line to which a plurality of storage lines are connected in the conventional manner is provided to only one side (for example, only right-side picture frame region), the storage lines cross the gate lines and the pull-around lines thereof. Accordingly, it is necessary to form lines as different layers to make the storage lines get over the gate lines and the pull-around lines. In this case however, the disconnection is liable to occur at the get-over portions and this constitutes a factor which impedes the enhancement of reliability.
Further, when the gate lines and the storage lines are made of aluminum or the like and are respectively subjected to anodization (anodic oxidation), since these lines get over each other, it is necessary to separately form these lines and this increases the process in number and becomes one factor which pushes up the manufacturing cost.
Accordingly, it is an object of the present invention to provide a display device of high display quality which can enhance the reliability such that even when gate lines are pulled out at both left and right picture frame regions, it is possible to provide a wiring pattern with no get-over portions between a gate wiring pattern which is constituted of gate lines and gate-line pull-around lines and a storage wiring pattern which is constituted of storage line and a common line which connect storage lines to each other.